Apparatus and process for making cement



July 4 33- D. c. couLsoN 1,916,417

APPARATUS AND PROCESS FOR MAKING CEMENT VF'lQd June 29, 1928 l 251166135-5116913 l' AAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA 'lNvENToR July 4, 1933- Y D. c. cOULsoN 1,916,417

APPARATUS AND PROCESS FOR MAKING CEMENT Filed June 29, 192s 2shets-sheet .2

Patented July 4, 1933 UNITED STATES PATENT oFFl'cE DONALD o. coULsoN, orCHICAGO, ILLINOIS, Assrenon, BY MESNE ASSIGNMENTS, 'ro

OLIVER UNITED FILTERS, INC., OF SAN FRANCISCO., CALIFORNIA, ACORPORATION 0F NEVADA Application ined rune as,

This invention relates to improvements in a part of the process employedin the formation of cementl by the so-called wet process andparticularly relates to the treatment or" the cement slurry before it isfed into the tiring kiln.

The principal object of this invention is to providegreater capacity anda more eilicient method and means for producing cement by the so-calledwet process whereby the usually wasted iue dust and kiln heat may beconserved and reused.

A further object of this invention is to provide a means whereby thecapacity of a continuous lter, which is used between' the slurryreservoir and the tiring kiln to remove thewater and conserve the heatnecessary to burn the material, is greatly increased.

f It is another object of this invent-ion to provide means forconserving the flue dust which is ordinarilylost and wasted in thewet-process ormaking cement and returning it back into the system.

It is still another object of the invention to provide a process forconserving flue dust and reintroducing it into the wet process systembetween the slurry reservoir and the continuous filters to increase thecapacity of the filters without substantial lossand Without-seriousoperating difficulties. i

Itis still another object of this invention to provide a process wherebythe slurry -fed into a continuous filter is heated by the waste heatavailable in a cement plant in order to greatly facilitate the removalof moisture from the slurry and thereby increasing'the capacity of theplant.

It is still another object of this invention to provide a processwhereby the filtration capacity of a continuousfilter interposed between-the slurry reservoir and the firing kiln 'may be greatly increased bthe conservation APPARATUS AND PROCESS FOR MAKING CEMENT 1928. SerialNo. 289,297.

a cement mill showing the manner in-which flue dust may be reclaimed andreturned to the system and in which the slurry may be heated, and

Fig. 2 is a diagrammatic'layout of a modiied form of the process showingthe plurale.

ity of points from which Waste heat may be taken for increasing thecapacity of the filter.

The so-called wet process of making hydrauli(l cement fumlamentallycomprises the introduction of the certain necessary raw materials into araw v{ ,rrirxdimc mill 410, together Gil with water from a tank 12which, according to this process, is preferably hot water.`

After the customary grinding and regrinding the mixture with the Water aslurry 1s formed which 1s passed into the mixing basln 14, through theconduit 16. This mixing' basin is provided with an agitator or paddle18, which may be continuously revolved by any desirable means (notshown). F rom the mixing basin or tank 14, the slurry is then pumped bythe slurry pump 20 into the mud drum of a continuous filterv 22. Theprocess ismore clearly shown and claimed in the apinto the kiln andproviding a more uniform product. This is more particularly dueto themethod i of operation of continuous filters which is well known incmumer'cial practice. and does not form a part of this invention.l.Thepresent invention ei'ects further economies in the process and asshown herein the discharge from the continuous filter 22 is fed by akiln feederA 24-into the kiln 26, it being understood that the moisturehas been .sufficiently reduced by the filter so that a substantially drycake is discharged forclinke'rmg. The upper end of the kiln 26 opensinto a dust chamber 28 which receives the gas and thedust theinirning-ozf'the.-4 cement cake and' this.-dust' collects in the'.

. chamberior` chambers where it will drop "into the screw conveyor{iO-or other suitand stray particles allowing the-final dust to' passinto the hopper 39,1 and theninto the -n'omixiug basin or tank 14 to bemixed'with the.

fable dev-lecto be removed. With'the present Processes of mixing cement,the dust that colects may amount to considerable, avera in from19.150137 tons forfeach- 1,000 barre s o -cement made, andl inmany-instances ,this is .entirely wasted.- The:4 screw conveyor 30conveys the 'collected ue dust'to the .dust

glvator 32lbyjwhich. it is liftedhto a hopper 3i/8 mesh. Thislrem'mesfthe Aoversize vdust wet slurry.` The flue dust which isrecovered from the`dust chamber .isintroduced may intothe mixing basinwhich isprovided with vthe necessary.v agitator to preventJ settling andto insure .an intimate mix withthe slurry. .from -thegrindingmi1l,.it.-will be under-'p stood, however, that this dustmaylbe `iI 1troduced at any other pointin the process an'dintimately mixed withthe'slurry' o r -introduced in the raw mill. 4'Iheexcess water the moistureof the'iilter cake. j

present also prevents the tendency 'of the slurf l and' dustto vset andadditionalwater added if desired'` [This excess water may desi-rably'bedravvnfrom the continuous filter 22 through the conduit 40.. The intro-.duction of the recovered ue 4dust into the slurry before the slurrypasses through the Afilter, increases the -ilter 'capacity andfpreventecloggingof the. filterl clothd or ,other difficulties inthe reservoirs.f It has been found in-.practicethatadding- I the flue dust into thefilter material not only 'leads to the recovery of the flue dustl itself"teroontainedjis incre thanoifset thereby.;

The reason for this peculiar .e'ject o ffthe Lilufe .dust'on the ltercapacity i's'not butA it has been'foun'dthat the 'eectsj dore?.

AOne explanation-is that cement slurryis made up of solidsanda liquid,the solids# v' 'is increased clation are thesolub e salts which form an1M-,folate elution. invasi ed which..

. but also increases'the capacity of the lter Vnot uncommonly from .65to 109%; due tothe peculiar'action of the flue' dust. Itis some'-A'times necessary, ,h oweven: to increase the moisture 'contentfrom 1t'o' 2%, buit inyi'ew et' :the fact that .the capacity-of' the. lter -isso greatly increased,the` slight increase .of waranging from those thatlwillpass throu 'h gopmesh screeningon down tothe celloi al' materil. Thecolloidal material retards thel A filtrationV rate butis occulate'd Abysome' .chemical reagents whereby the' filtration rate .The re rate.

nts which cause fiocil tend 'to regulate the'hydrogen-i'on content ofTheautdustwhictis essentially the 'Solid part of .cement slurry, whichhas been heated i l'to a point 'of' ca lcnation, has changed fromlmentioned-above, giving a greater filtration I havealso foundthat therate 3f-filtrationils urther increased by hea-ting thel slurry 'by'introducing steam orhot Water coil .42

.into mixing tank. 14 todecreasefthe viscosity ofjthe .slurry 'edto thefilter', this .coil re- `ceivesh5t water from the economizerii a't-/tached to the .Waste heat boiler 46'adjacent the dust chamber 28.'--The circulation pump 47 is used to' insure a rapid exchangeor'- heat.

The slurry may, `l1owever be heated-inmany diiferent ways' fromV the.waste heat of 'thecement mill, as for examplei Steam may be 4takenlfromthe waste 'heat boiler 4G 'through the conduit 48 and introduced intethe'hot vivatertank' 12 to increase thetemperaturevof the slurrymixtureand to in-l I troduce hot slurry into-the filter) .|`This heat visnotonly conserved by its introduction to.

the slurry, but the hot slurry also increases' the c'apacityof thefilter, and tends toreduce It win thus be noted that thtpretiots'difficulties of addinglue dust to the slurrg whi'ch causedprematuresettng' or vhic was heretofore added to the :feedoithe kiln,and which .was Verydiilicu'lt to'controll and frequently causedmud'rings, have been ob- .viated by the. introduction ofthe lue dustfactorily operatewith. an excess off water when a continuous filter; isused'becauseis'uch a lteris not particularly eiected bythe previousamount of waterpresent.- In other '.1110 I w0rds,no matter how'muchwateris used `to Aprevent the-Hue dustfrom premature setting inthe mixingychamber, a uniform cake may formed-:havin moisture therein leinthe. r'

1 tinuo'us filter.: 'Tlxigddition of t 4A ue dust materiallyadds to theeiciency of the filter as before mentioned doubling the ordinary'capacity and in :additionv 'valuable cement making material isrecovered in the' dust..

The increase' in temperature-inthe slurry not increase moisture'necessary. because of ment is brought about'b' the conservation of on wA 'slightly modified :the .least .amount ofr. .con-

only'counteracts'the disadvantage of the small b f thehtmt and ue'dust w'ch'.-are always r; 'y t. "ent in 'maln'ng' lan'ts and which ave beenhereof v form of 'the device is shown in Eig',A 2in which raw grinding'mills* ter tank.

50, which'receive and grind the necessary solid-raw materials to therequisite neness, receive hot Water from the tank 51 through theconduits 52. The slurry is then forced through the/.conduit 53 into theslurry storage tank or kiln feed' tank 54 from which it ispumped'through the slurry pump 55, throughV heat exchanger 56 andconduit 57Ato the bottom of a continuous filter 58. This filter dis-`charges' through the Water. jacketed screw kiln 'feeder 59, into thekiln 60, openin into lthe dust chamber 62 which is provide with a Wasteheat boiler 64 and -econoniizers 65 and 66. The hot'water is tapped fromeither or both of the economizers 65 and 66 by thev conduit 67V and isintroduced into the hot Wa- Steam may also be ta ped from the Waste heatboilerfl and bemtroduced into,v the hot Water tank 51 by the conduit 68.The heat exchan er 56 receives its heat from the excess heat o thekilnthrough the necessary conduit 69.'

` In addition to the hot water which is mixed with the slurry, it mayalso be desirable to keep the slurryin a Warm condition b the necessaryhot Water coils 70 in the sliirry tank 54 which are supplied with hotWater from the economizer which is pumped throu h the circulating pump7l 'and conduits 2 through the coils. It is also possibleto yintroducesteam from the Waste heat boilcrfi' through the conduit 68 and theconduit 73 into the-slurry tank.

A further' source of hea-t is a Water jacket/ed kiln feed screw 59 whichreceives cold Water through the conduit 74 and discharges hot. -waterthrough the conduit 5 which may also preferably be introduced into thehot Water tank. The remaining sources of hot Water or steam are -onlysuggestive and it is obvious that in a cement plant there are manysources of heat otherwise Wasted, available. 4By using this Waste heatto heat the slurry, it is possible to form a drier cake and increase thefilter capaci-ty and this reduction in the moisture of the cake will'also cause a greater kiln l output with less fuel'. The filtrate fromthe filter may valso be discharged into the hot Water tank therebyconserving the possible" example, in the kiln feed, the kilncapacity isincreased, theue dust is advantageously used, and a more uniformcementis prof Y l duced.A The flue dustis the normally wasted product of thecement lant.

'A second feature of t e process is that the slurry is preferably heatedby the surplus or .Waste heat of the cement plant, and this increaseinslurry temperature also increases the capacity of the filters and thecement kiln and furthermore, counteracts the slight increase in moisturerequired when the flue dust is added. It is to be understood that theslurry may be heated directly 0r indirectly by many means, and either orboth of the two steps of the process may be used, as desired.

While. ll have shown preferred forms of embodiment of this process, itis understood that man v modifications may be made there-Y in, and ldesire a broad interpretation of my invention Within the spirit and scoof the disclosure and the claims appended creto.

I claim: 1. ln a process for making cement by the Wet process, With theaid of a continuous filter the method of increasing the filteringcapacity by adding flue dust to the slurr and subsequently passing'saidslurry throug a continuous'iilter.

2. In a process for makinfg cement by the wet process, the method oincreasin the filtration capacity which comprises adding flue dust tothe slurry adding additional Water to improve fiuidity of the mixtureand subsequently passing said slurry through a continuous filter.

3. The combination in a Wet rinding cement mill having a continuous lterfor reducing the moisture content of the ground slurry before it is fedinto the furnace, of a dust-collector for recovering lue dust from thekiln, a dust feeder to introduce said fiue v dust into the slurry,and aconduit and pump for -pas'sing the slurry and fiue dust to a continuouslter for dewatering.

4. 'llhe process of forming cement by wet grinding which comprisesgrinding'the solid materials with Waterto form a slurry, flocfculating'the slurry by adding flue dust therewill to, ltering the fiuedust and slurry lin a cont-inuous filter and feedingthe filter *cake to.

the kiln. y

' 5. Thecombination in a wet grinding. cement mill having a continuousfilter for re ducing the moisture content of. the ground' slurry beforeit is fed into the furnace, of adust collector Ifor collecting flue dustfroml said furnace, a conveyor` for introducing flue ldust into theslurry, a mixing tank for mixing said slurry and dust, heated 'conduitsheated by Waste heat fromA said furnace-'and pump 'means to Apumpsaidslurry through said conduits to counteract the increase in moistureeect dueto the addition of the fiue dust. g

6. The process of making raw cement mix which comprises grindingthe rawmaterials with an excess of Water, adding fine dustto the slnrrythusformed, heatingthe slurryV -4and. 'assing the heated slurry intocontinuous lters. I f

7. Thelprocess of forming cement 'by wet grinding 'which comprisesgrinding the' 'solid material with water to form a slurry adding fluedust tol the slurry; heating the ue dust and slurry mixture to increasethe filtering capacity, filtering .the fine dust and slurry-in acontinuous filter' and'feeding the filter cakeV to the kiln.

in a wet fss' ltrerv 'A 9. The method of forming oement by'a wivet@easing v the V1a continuons 1 grinding process 'whichl comprisesgrinding h solid .constituents with hot water to .formv a slurry,.heating the slurry, recovering flue' dust from the kiln, addingfiue'fdu'st to the capacity, and passim' the slurry through'a continuousfilter to ewater the same',fand

feeding the filter 'cake *to thekiln.

In testimony-mman have aixedmy .svignatnre tothis Specification.

DONALD o. (loonsom .slurry before filtration to inrease filtering l

